Tubulous vapour generators



Nov. 10, 1964 R. E. ZOLLER TUBULOUS VAPOUR GENERATORS 5 Sheets-Sheet 1 Filed May 2. 1961 FIG.1

INVENTOR. Ronald E. Zoller ATTORNEY Nov. 10, 1964 R. E. ZOLLER TUBULOUS VAPOUR GENERATORS 5 Sheets-Sheet 2 Filed May 2, 1961 FIG.2

LKIELL Err? FIG. 3

Err IE hi Va TTTIJ H 4 I I I IIL FIG.8

INVENTOR Ronald E. Zoller AT TO RNEY Nov. 10, 1964 R. E. ZOLLER 3,156,219-

TUBULOUS VAPOUR GENERATORS Filed May 2. 1961 5 Sheets-Sheet 4 uvvmrox Ronald E. Zoller Nov. 10, 1964 R. E. ZOLLER TUBULOUS VAPOUR GENERATORS 5 Sheets-Sheet 5 Filed May 2. 1961 FIG.9

INVENTOR.

Ronald E. Zoller ATTORNEY United States Patent 3,156,219 TUBULOUS VAPOUR GENERATORS Ronald E. Zoller, London, England, assignor to Babcock & Wilcox Limited, London, England, a British company Filed May 2, 1961, Ser. No. 107,165 Claims priority, application Great Britain May 2, 1960 6 Claims. (Cl. 122-510) This invention relates to tubulous vapour generators. In power plants for central electricity generating stations, the capacity of vapour generating units has become progressively larger with consequent increased furnace Width and length of vapour and liquid drum. With downcorners at the ends of the vapour and liquid drum of a vapour generator, longitudinal flow of liquid to the ends of the drums must occur. Longitudinal flow of liquid within the drum may be reduced by distributing a series of downcomers along the length of the drum, but in a large boiler having a furnace chamber with a width, for example, of well over one hundred feet, supply tubes taken round the sides of the vapour generator from the downcomers to distributor headers for the wall tubes of the furnace chamber wall remote from the downcomers are of necessity long and expensive to provide and their differing lengths render difficult the attainment of a sufiiciently uniform circulation through the said wall tubes. Moreover, in considering the problem of longitudinal flow of liquid in the vapour and liquid drum, there are still the discharges from the Wall tubes of the furnace chamber side walls to be taken into account.

By the present invention we provide a tubulous generator with a furnace chamber having walls lined by upright vapour generating tubes and a hopper bottom, burners arranged to discharge into the furnace chamber and a gas pass leading from the furnace chamber, an elevated drum containing a liquid space and extending horizontally and parallel to the front and rear walls of the furnace chamber and a series of downcomer tubes distributed along the drum, connected with the liquid space within the drum, extending downwardly in the neighborhood of one of the said walls and arranged to supply liquid to tubes lining the said wall and the subjacent hopper wall and also to supply liquid to tubes lining the opposite wall and the hopper wall subjacent to that wall through tubular means extending adjacent to and above the bottom of the hopper from one side to the other side of the hopper.

Advantageously, the tubular means comprise a plurality of groups of tubes which extend through the hopper or between sections of the hopper, each group is supported by downward extensions of front and rear wall tubes and is adapted to act as a beam and adjacent groups carry beams extending therebetween and serving as hopper support means.

The invention will now be described by way of example with reference to the accompanying partly diagrammatic drawings, in which FIGURE 1 is a side elevation, in section on the line II of FIGURE 2, of a natural circulation steam generator furnace chamber and associated lateral gas passes;

FIGURE 2 is a plan view of the furnace chamber and lateral gas passes; FIGURE 3 is a plan view through part of the steam generator furnace chamber in section on the line IIIIII V of FIGURE 1;

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FIGURE 4 is a front elevation of the left half of the furnace chamber, parts being broken away;

FIGURE 5 is a diagram of the arrangement of water supply tubes adjacent to the left half of the hopper bottom of the furnace chamber;

FIGURE 6 is a side elevation, in section on the line VIVI of FIGURE 5, of the hopper bottom of the furnace chamber, the scale being larger than that of FIGURE 1;

FIGURE 7 is a pictorial representation of the relative arrangement of certain tubes at the hopper slag outlet;

FIGURE 8 is a side elevation of part of the length of a beam formed by vertically aligned water supply tubes;

FIGURE 9 is a sectional side elevation of the hopper bottom of a furnace chamber in which supply water is led through the hopper slag outlet, from front to rear thereof, in a modified manner; and

FIGURE 10 is in its left-hand half (FIGURE l0(a)) a front elevation of the parts shown in FIGURE 9 in section on the line Xa--Xa of FIGURE 9 and in its righthand half (FIGURE 10(b)) a similar elevation but in section on the line Xb-Xb of FIGURE 9.

Referring to FIGURES 1 to 7 of the drawings, the furnace chamber 1 of a natural circulation tubulous steam generator is defined by a vertical front wall 2, a vertical rear wall 3 and by vertical side walls 4. The furnace chamber is several times wider than the distance between the front and rear walls, for example feet between side walls and 30 feet between front and rear walls. The furnace chamber is fired by pulverised coal burners 5 arranged to discharge into a lower region of the furnace chamber from the front wall 2 thereof. A pair of lateral gas passes 6 extend rearwardly from an upper region of the furnace chamber, which contain superheating surfaces 7 and which lead to respective down passes (not shown) containing further superheating surfaces, reheating surfaces and economiser surfaces: between the two lateral passes 6 is an access space 8 bounded forwardly by a front wall 9 which is in a vertical plane about half way between the front and rear walls 2 and 3 and bounded laterally by side walls 10. Radiant superheating platens 11 are provided in the upper region of the furnace chamber.

The furnace front wall I2 is cooled by steam generating tubes 12 extending from a lower header 13 to an upper header 14. The furnace rear wall 3 is cooled by steam generating tubes 15 which extend from a lower header 16; some of the tubes 15 extend forwardly from the top of the rear wall 3 to form the floor 17 of the access space 8 and the front wall h thereof and extend in the furnace chamber roof 1% to an upper header 21, others of the tubes 15 extend vertically through the gas passes 6 to upper headers 22, and the remainder of the tubes 15 form arches 23 below the respective gas passes 6 and form floors 24 thereof and extend finally as vertical screens to upper headers 25. The remainder of the roof is and the roofs of the lateral passes 6 are lined by superheater tubes (not shown).

The furnace side walls 4 are cooled by steam generating tubes 26 extending from lower headers 27, 28 and 29 to upper headers 36. In the side wallsli) of the access space 3 are steam generating tubes 31 which below the said space extend in the furnace chamber adjacent the rear wall 3 thereof in a pair of centre side walls 32 which are parallel to the furnace side walls 4; the tubes 31 spring from lower headers 33 and terminate in upper headers 34.

The steam and water mixtures delivered to the various upper headers 14, 21, 22, 25, and 34 are passed by suitable connectors (not shown) to a steam and water drum 35 the axis of which extends parallel to and to the front of the furnace front wall 2, and which supplies to a series of twelve vertical downcorner tubes A to L, subsequently referred to in more detail, the water required by the lower headers 13, 16, 27, 28, 29 and 33.

The furnace chamber has a hopper bottom comprising a downwardly and rearwardly inclined front hopper wall 41 subjacent the furnace front wall 2 and a downwardly and forwardly inclined rear hopper wall 42, the hopper walls 41 and 42 leading to the bottom part 43 of the hopper which constitutes a slag outlet the axis of which is inclined forwardly and downwardly.

Referring to FIGURE 6, the front wall 44 of the slag outlet 43 and the front hopper wall 4-1 are cooled by tubes 12 of the superjacent furnace front wall 2 and the rear wall 45 of the slag outlet 43 and the rear hopper wall 42 are cooled by tubes 15 of the superjacent furnace rear wall 3. Below the slag outlet 43 slag quenching and slag removal means 46 of known kind are provided.

The tubes 12 at the bottom of the hopper front wall 41 are inclined forwardly and downwardly substantially parallel to the hopper rear wall 42 to define the front wall of the slag outlet 43 and below the slag outlet the tubes 12 are taken forwardly to the header 13 which lies vertically below the front wall 2. Every fifth tube 12a of the front wall 2 extends vertically downwardly from the said wall to connect at its lower end into the header 13 which is supported by the tubes 12a. in order to support the tubes 12 at the front of the hopper inclined buckstays 51 are distributed along the front of the hopper outside the furnace chamber, each buckstay being pivoted at its upper end 52 to a horizontal buckstay 53 carried by the furnace chamber wall tubes 12 and common to all the buckstays 51 and being connected at its lower end 54 to a horizontal beam 55 which is common to a number of buckstays 51 and which is supported by means to be described. The inclined buckstays 51 are provided with supporting means for the tubes 12 of the hopper front wall -1 in the form of l-beams extending between adjacent inclined buckstays 51, one of the flanges of each I-beam 56 being embraced by slotted parts 57 of brackets 58 secured to tubes 12 in the hopper front wall 44 and the slots 57 being dimensioned to permit differential thermal expansion between the inclined buclcstays S1 and the said tubes.

The tubes 15 at the bottom of the hopper rear wall 42 continue downwardly at the rear of the slag outlet 43 at first with no change of direction and then vertically and below the outlet 43 the tubes extend rearwardly to the header 16 which is positioned intermediate the slag outlet and the of the rear wall 3. Every fifth tube 15a of the wall 3 extends vertically downwardly from the said wall to the level of the slag outlet 43 and then forwardly and downwardly to connect with the header 16. In order to support the tubes 15 at the rear of the hopper inclined buclrstays 5% are distributed along the rear of the hopper outside the furnace chamber, each buclrstay being pivoted at its upper end 69 to a horizontal buclrstay 61 carried by the furnace chamber wall tubes 15 and being connected at its lower end 62 to a horizontal beam 63 which is supported by means to be described; transoms 5d and slotted brackets 58 are provided for the buckstays 59 as for the buckstays 51.

The downcorner tubes A to L are distributed along the length of the drum 35. In order to accommodate the burners 5 in the front wall 2 of the furnace chamber, the downcomer tubes are pitched apart alternately through smaller and greater ditsanccs. The downcomer tubes terminate in respective upright distributors '71 at the level of the hopper slag outlet Q3 and connector tubes or sets of connector tubes lead in the manner that will be described from the distributors 71 to the said lower headers 13, 1d, 27, 25$, 29 and 33.

Referring to FIGURE 5, the front wall lower header 13 is sectionalised by diaphragms 72 into twelve sections 13A, 13B, 13C and the first section 13A thereof is supplied with water from the distributor 71 of the first downcomer tube A through a set of five connector tubes A1, the ends of which in the header section 13A are distributed along the length of the section; similarly, the second header section 13B, the third header section 13C are respectively supplied from the distributors of the second downcomer tube B, the third downcomer tube C through sets of five connector tubes B1,

The lower headers 27, 28 and 29 for each furnace side wall 4 are supplied from the four downcomer tubes nearest the side wall. Of the said three headers, the header 28 is a main header disposed at the level of the bottom of the hopper 40, the header 27 is a smaller header nearer the front wall 2 than the header 28 and at a higher level than the header 23 while the header 29 is a smaller header nearer the rear wall 3 than the header 28 and at a higher level than the header 28. Referring to the headers for the side wall nearest the first to fourth downcomer tubes A, B, C and D, the main header 28 is sectionaliscd by diaphragms 73 into a relatively small front end section 281), a front main section 28C, a rear main section 28B and a relatively small rear end section 23A. The main header front end section 28D is supplied from the distributor 71 of the fourth downcorner tube D by a connector tube D-2 which leads laterally in front of the distributors 71 and then rearwardly at the side of the steam generator; the front smaller header 27 is supplied from the distributor 71 of the fourth downcomer tube D by a set of two connector tubes D4; the front main section 28C of the main header 28 is supplied from the distributor 71 of the third downcorner tube C by a set of three connector tubes C4; the rear main section 28B of the main header 28 is supplied from the distributor 71 of the second downcomer tube B by a set of three connector tubes 8-2; the rear end section 28A f the main header 28 is supplied from the distributor 71 of the first downcomer tube A by a connector tube A-3; and the rear smaller header 2h is supplied from the distributor 71 of tne first downcomer tube A by a set of two connector tubes A4.

The rear wall lower header 16 is sectionaliscd by diaphragrns 74 into twelve sections 16A, 16B, 16C of which the first section 16A is supplied from the distributor 71 of the first downcomer tube A by a set of five connector tubes A2 which lead laterally from the distributor '71, then rearwardly at he side of the steam generator, then laterally behind the plane of the rear wall 3 and finally forwardly to the header section 16A in which their ends are distributed along the length of the said section.

The second and third rear header sections and 16C are supplied from the distributors 71 of the second and third downcomer tubes B and C by respective sets of connector tubes B3 and C3 which are led through the hopper slag outlet 43 in a single group 75 of ten tubes extending from the space in front of the hopper to the space behind the hopper 4-9. Similarly, the fourth and fifth rear header sections 15D and ME are supplied from the distributors 71 of the fourth and fifth downcomer tubes D and E by respective sets of five connector tubes D-4 and E2 which are led through the hopper slag outlet 43 in a single group 7-6 of ten tubes. A set of three connector tubes 13-3 and a set of two conr .tor tubes E-d from the distributor 71 of the fifth doc/n corner tube E and a set of three connector tubes F2 and a set of two connector tubes F4) fromthe distributor r ruth header section 16E, the connector tubes F3 are led to the sixth header section 16F, while the connector tubes E-3 are led to one and the connector tubes F-2 are led to the other of a pair of headers 33 from which extend upwardly through the hopper rear wall 42 the tubes 31 of one of the pair of centre side walls 32.. A set of five connector tubes F-4 from the distributor 71 of the sixth downcomer tube F and a set of five connector tubes G-2 from the distributor 71 of the seventh downcomer tube G are led in a single roup 78 of ten tubes through the hopper slag outlet 43 and deliver water respectively to the sixth and seventh rear header sections 16F and 16G. The tube group 75 is at an eighth, the tube group 76 at a quarter, the tube group 77 at three-eighths and the tube group 73 at one-half of the distance from one end of the hopper 40 to the other.

The tube groups 75, 76, 77 and 73 and the remaining tube groups (not shown) are similar and are similarly supported. Referring to FIGURE 6 and to FIGURE 7, which latter illustrates an upper portion of tube group 76, the connector tubes comprising the group 76 are vertically aligned, the five tubes D4 alternating with the five tubes E-2. In front of the hopper 40 the tubes are secured in a holder 81 slung from a horizontal chem-- nel member 82 which is supported by several of the tubes 12a, which for the purpose of supporting the channel member 82 are provided with diametrically opposite pairs of lugs 84. Similarly behind the hopper 40 the tubes 15a are secured in a holder 85 slung from a horizontal channel member 36 which is supported by several of the tubes 15a, which for the purpose of supporting the channel member 86 are provided with diametrically opposite v pairs of lugs 87. For the accommodation of the tube group 76 where it penetrates the rear wall of the hopper slag outlet 43 a pair of tubes 15b of the tubes 15 instead of continuing downwardly from the bottom of the hopper rear wall 42 extend forwardly side-by-side above and adjacent the uppermost tube of the group and connect with the distributor 71 of the downcomer tube D. For the accommodation of the tube group 76 where it penetrates the front wall of the hopper slag outlet 43 a pair of tubes 12b of the tubes 12, instead of being led forwardly and downwardly in the front wall of the hopper slag outlet 43 are led forwardly above and adjacent the tubes 15!; and are taken down at opposite sides of the tube group 76 to the front wall lower header 13.

Each of the tube groups 75, 76, 77 and 78 acts as a beam and supported thereby by any suitable means (not shown) such as by brackets secured to plates welded to the tubes are the adjacent ends of the beams 55 and 63 previously referred to. Each beam is supported at its ends by adjacent tube groups or by the end tube group 75 and the tubes 26 of the adjacent side wall 4. The connection at the lower end of each inclined buckstay 51 with the appropriate beam 55 is a pin and slot connection permitting differential thermal expansion of the buckstay 51 and the connection at the lower end of each inclined buckstay 59 with the appropriate beam 63 is a pin and slot connection permitting differential thermal expansion of the buckstay 59. Each beam 55 supports tubes 12 of the slag outlet front wall 44 through brackets 79 and each beam 63 supports tubes 15 of the slag outlet rear wall 45 through brackets 80.

The rear wall lower header 16 is supported from beams 88 each of which is supported at its ends by adjacent tube groups or by the end tube group 75 and the tubes of the adjacent side Wall 4; the means (notshown) for supporting the beam ends may comprise brackets secured to plates welded to the tubes.

Means may be provided for stiffening the beam constituted-by a tube group. Referring to FIGURE 8, for example, such means may be provided by plates 91 welded .to all of the tubes or/ and fillet rods 92 each welded to two adjacent tubes, and such plates or rods may be provided on one or both sides of the tube group.

It will be understood that the arrangements of connector tubes are similar in the right-hand half of the furnace chamber as in the left-hand half of the furnace chamber.

It will be seen that each downcomer tube supplies water to an adjacent section of the front wall lower header 13. Preferably, the front wall upper header 14 is sectionalised similarly to the header 13 and the steam and water mixtures from the upper header sections are led to respective lengths of the drum from which the respective downcomers withdraw water. Similarly, each downcomer tube supplies water to an adjacent section of the rear wall lower header 16 and preferably it is arranged that the steam and water mixtures generated in the tubes 15 fed by each header section are led to that length of the drum from which the corresponding downcomer tube draws water. Each downcomer tube also supplies water to a section of the tubes of a side wall 4 or of a centre side wall 31 and preferably the steam and Water mixtures generated in each wall section are led to the appropriate length of the drum, for example, steam and water mixtures generated in the side wall tubes 4 springing from the rear main section 28B of the main side wall header 28 are preferably led to the length of drum from which the downcomer tube B issues. Thus, for example, the length of drum adjacent the downcomer tube C receives water and steam mixtures through connectors (not shown) from a section 140 of the upper header 14 corresponding to the section 13C of the lower header 13, from sections 22C and 25C of the upper headers 22 and 25 corresponding to section 16C of the lower header 16 and from section 30C of the upper header 30 corresponding to section 28C of the lower header 28.

Since the liquid that flows from the drum at any location through a downcomer tube is returned as vapour and liquid mixtures to the same location, large longitudinal flows of liquid within the drum are avoided.

With the arrangement described, an effective and economical hopper support is obtained and although the tube groups pass through the hopper the vertical alignment of the tubes of the groups and adequate spacing between the groups avoid objectionable obstruction within the hopper. At the same time undesirable heating of the tubes of the groups is avoided since the lengths thereof Within the hopper are small and the lengths are large ly screened from radiation by the superjacent tubes taken from the rear wall of the hopper and by the part of the front hopper wall above the groups of tubes which overhangs the slag outlet.

Referring to FIGURES 9 and 10, a modification is indicated in which the lower end length 191 of a downcomer tube, which is assumed to extend vertically downwardly from an upper drum at the front of the steam generator, extends horizontally rearwardly through the slag outlet 43 of the hopper 40 within a space 102 formed by certain of the tubes 12 and 15 of the hopper walls. A band of twenty-two adjacent tubes 150 of the slag outlet rear Wall 45 are taken forwardly across the slag outlet 43 to and through theslag outlet front wall 44, leaving the said rear wall at diiferent heights so that they extend across the slag outlet in inverted V-forrnation. In order to permit passage of the band of tubes 150 through the front wall 44 of the slag outlet a bank of twenty-two adjacent tubes 120 are taken forwardly from the said wall, also in inverted V-formation. Each of the twenty uppermost tubes of the bank 150 has beside it a tube of the band 12c, the latter tubes inhibiting downward furnace radiation through the spaces between adjacent tubes of the bank 150. Within the sheltered channel of inverted V-shape so formed extends the downcomer end'length 101 which is arranged to lead to the rear of the hopper supplywater for adjacent lower header sections for steam generating furnace rear wall tubes. The tubes are taken outwardly at their front end portions in opposite directions and are connected to a pair of vertical headers 13x. The tubes 150 are also taken outwardly at their front end portion in opposite directions and are connected to a pair of vertical headers 16x located between the pair of headers 13x. The space 102 may serve for the passage to the rear of the hopper of more than one downcomer tube extension 101.

What is claimed is:

1. In combination with a vapor generator, walls including vapor generating tubes forming an upright furnace confining high temperature gases and a hopper opening to the lower end of the furnace, said walls including a pair of opposed walls diverging in an upward direction to form a part of the hopper and then extending upwardly to form a part of the furnace; means supplying fluid to the vapor generating tubes of said opposed walls including a drum containing a water space, a series of downcomer tubes connected to said drum at spaced positions along the length thereof, and means connecting said downcomer tubes to the vapor generating tubes of said opposed walls and including tubular means extending through said hopper and the opposed walls thereof; and means for supporting said hopper including means transmitting the weight of said hopper to vapor generating tubes of said opposed walls of the furnace, said last named means including means for transmitting the weight of said hopper to and carrying said hopper from said tubular means, and means for top-supporting said tubular means from some of the vapor generating tubes of said opposed walls of the furnace.

2. In combination with a vapor generator, walls including vapor generating tubes forming an upright furnace confining high temperature gases and a hopper opening to the lower end of the furnace, said walls including a pair of opposed walls diverging in an upward direction to form a part of the hopper and then extending upwardly to form a part of the furnace; means supplying fluid to the vapor generating tubes of said opposed walls including a drum containing a water space, a series of downcomer tubes connected to the Water space of said drum at spaced positions along the length of the drum, and means connecting said downcomer tubes to the vapor generating tubes of said opposed walls and including a plurality of groups of tubes extending through said hopper and the opposed walls thereof; and means for supporting said hopper including means transmitting the weight of said hopper to vapor generating tubes of said opposed walls of the furnace, said last named means including means for transmitting the weight of said hopper to and carrying said hopper from said groups of tubes, and means for top-supporting said groups of tubes from some of the vapor generating tubes of said opposed walls of the furnace.

3. In combination with a vapor generator, walls including vapor generating tubes forming an upright furnace confining high temperature gases and a hopper opening to the lower end of the furnace, said walls including a pair of opposed walls diverging in an upward direction to form a part of the hopper and then extending upwardly to form a part of the furnace; means supplying fluid to the vapor generating tubes of said opposed walls including a horizontal drum containing a water space and disposed at a level above said hopper, a series of downcomer tubes connected to the water space of said drum at spaced positions along the length of the drum, and means connecting said downcomer tubes to the vapor generating tubes of said opposed walls and including a plurality of groups of tubes extending th ough said hopper and the opposed walls thereof, with the tubes of each group being vertically aligned; and means for supporting said hopper including means transmitting the weight of said hopper t0 vapor generating tubes of said opposed walls of the. furnace, said last named means including means for transmitting the weight of said hopper to and carrying said hopper from said groups of tubes, and

means for top-supporting said groups of tubes from some of the vapor generating tubes of said opposed walls of the furnace.

4. In combination with a vapor generator, walls including vapor generating tubes forming an upright furnace confining high temperature gases and a hopper opening to the lower end of the furnace, said walls including a pair of opposed walls diverging in an upward direction to form a part of the hopper and then extending upwardly to form a part of the furnace; means supplying fluid to the vapor generating tubes of said opposed Walls including a drum containing a water space, a series of downcomer tubes connected to said drum at spaced positions along the length thereof, and means connecting said downcomer tubes to the vapor generating tubes of said opposed walls and including a plurality of groups of tubes extending through said hopper and the opposed walls thereof; and means transmitting the weight of said hopper to vapor generating tubes of said opposed walls of the furnace including means transmitting the weight of said hopper to and carrying said hopper from said groups of tubes, said last named means comprising buckstays extending along and outside of the opposed walls of said hopper and secured to the vapor generating tubes thereof, and beams supporting said buckstays and connected to said groups of tubes, and means for top-supporting said groups of tubes from some of the vapor generating tubes of said opposed walls of the furnace.

5. In combination with a vapor generator, walls including vapor generating tubes forming an upright furnace confining high temperature gases and a hopper opening to the lower end of the furnace, said walls including a pair of opposed walls diverging in an upward direction to form a part of the hopper and then extending upwardly to form a part of the furnace; means supplying fluid to the vapor generating tubes of said opposed walls including a drum containing a Water space, a series of downcomer tubes connected to said drum at spaced positions along the length thereof, and means connecting said downcomer tubes to the vapor generating tubes of said opposed walls and including a plurality of groups of tubes extending through said hopper and the opposed walls thereof, with the tubes of each group being vertically aligned; and means for supporting said hopper including means transmitting the weight of said hopper to vapor generating tubes of said opposed walls of the furnace, said last named means including means for transmitting the weight of said hopper to and carrying said hopper from said groups of tubes, and means for top-supporting said groups of tubes from some of the vapor generating tubes of said opposed walls of the furnace; some of the vapor generating tubes of one of the opposed walls of said hopper being bent out of the plane of said one wall so as to extend directly over and adjacent to said groups of tubes to screen said tube groups from the furnace gases.

6. in combination with a vapor generator, walls including vapor generating tubes forming an upright furnace confining high temperature gases and a hopper opening to the lower end of the furnace, said Walls including a pair of opposed walls diverging in an upward direction to form a part of the hopper and then extending upwardly to form a part of the furnace; means supplying fluid to the vapor generating tubes of said opposed wall including a drum containing a water space, a series of downcomer tubes connected to said drum at spaced positions along the length thereof, means connecting said downcomer tubes to the vapor generating tubes of said opposed walls and including tubular means extending through said hopper and the opposed walls thereof, and means dividing the vapor generating tubes of each of said opposed walls into groups and cooperating with said tubular means and downcomer tubes so that fluid supply to and discharge from each tube group occurs in the same portion of the drum; and means for supporting said hopper including means transmitting the Weight of said hopper to vapor generating tubes of said opposed walls of the furnace, said last named means including means for transmitting the Weight of said hopper to and carrying said hopper from said tubular means, and means for top-supporting said tubular means from some of the vapor generating tubes of said opposed walls of the furnace.

References Cited in the file of this patent UNITED STATES PATENTS Ely July 25, 1933 Drewry June 3, 1941 Rehm Oct. 20, 1942 Schoessow Jan. 29, 1952 Coughlin Aug. 7, 1956 Walter et a1. Dec. 11, 1956 Koch et a1. Aug. 9, 1960 FOREIGN PATENTS German patent application C9972 IA/13 g, Jan. 19, 

1. IN COMBINATION WITH A VAPOR GENERATOR, WALLS INCLUDING VAPOR GENERATING TUBES FORMING AN UPRIGHT FURNANCE CONFINING HIGH TEMPERATURE GASES AND A HOPPER OPENING TO THE LOWER END OF THE FURNANCE, SAID WALLS INCLUDING A PAIR OF OPPOSED WALLS DIVERGING IN AN UPWARD DIRECTION TO FORM A PART OF THE HOPPER AND THEN EXTENDING UPWARDLY TO FORM A PART OF THE FURNACE; MEANS SUPPLYING FLUID TO THE VAPOR GENERATING TUBES OF SAID OPPOSED WALLS INCLUDING A DRUM CONTAINING A WATER SPACE, A SERIES OF DOWNCOMER TUBES CONNECTED TO SAID DRUM AT SPACED POSITIONS ALONG THE LENGTH THEREOF, AND MEANS CONNECTING SAID DOWNCOMER TUBES TO THE VAPOR GENERATING TUBES OF SAID OPPOSED WALLS AND INCLUDING TUBULAR MEANS EXTENDING THROUGH SAID HOPPER AND THE OPPOSED WALLS THEREOF; AND MEANS FOR SUPPORTING SAID HOPPER INCLUDING MEANS TRANSMITTING THE WEIGHT OF SAID HOPPER TO VAPOR GENERATING TUBES OF SAID OPPOSED WALLS OF THE FURNACE, SAID LAST NAMED MEANS INCLUDING MEANS FOR TRANSMITTING THE WEIGHT OF SAID HOPPER TO AND CARRYING SAID HOPPER FROM SAID TUBULAR MEANS, AND MEANS FOR TOP-SUPPORTING SAID TUBULAR MEANS FROM SOME OF THE VAPOR GENERATING TUBES OF SAID OPPOSED WALLS OF THE FURNACE. 